Designers of test and measurement equipment face a variety of challenges in creating cables and connectors that form probes for interfacing with a device under test (DUT). Designers are always trying to fit an ever-increasing number of connections into a constantly decreasing area on the DUT for interfacing. At the same time, the signaling rate and frequency content of the signals being probed is also increasing. This presents several challenges to the designers of such probes.
For example, it has proven difficult to provide a highly compact array of connections that minimize the footprint and at the same time place probe tip networks, such as isolation circuits, extremely close to the pads of the grid array on the DUT. More specifically, manufacturers of devices being tested with such probes desire an array having a center-to-center distance of less than 1 millimeter. Further, when such probes are used to transfer high bandwidth (greater than 1 Ghz) signals, signal isolation and signal fidelity become a problem, especially when attempting to interface with a large number of signals (greater than 100) in a small area (less than 0.25 sq. in.). It has also proven quite difficult to minimize the capacitive loading of the probe, to less than 1 pF per signal, on a DUT with such a great number of connections. Finally, it is desirable that probes have a minimal electrical transmission line stub length between the probed pad and the isolation components minimizing the effects of the probe on the high-speed signals of the DUT.
The Inventors of the present invention have determined a need for a probe that increases the density of connections, while minimizing capacitance loading and stub length while maximizing usability of the probe.